Direct reading hand micrometer



March 24, 19.59 w. F. JOHNSON DIRECT READING' HAND MICROMETER Filed Aug. 5, 1954 1N V EN TOR. f te?? :JUA/Meow, BY Z E V fx1-Ton wa-Ys.

Unite The invention relates to instruments for precision measurement, and embodies, more specifically, an improved form of hand micrometer.

One object of this invention is 'to provide a hand micrometer with a novel form of plus or minus scale for easy, direct, and accurate measurements without necessitating visual interpolation between scale divisions.

Another object of this invention is to provide a hand micrometer having the above advantage but of simplified construction, for ease of manufacture at a substantially reduced cost.

The foregoing and other objects of the invention, which will be set forth hereinafter or will be 'apparent to' one skilled in the art upon reading these specications, are accomplished by that construction and arrangement of parts of which I shall now describe an exemplary embodiment. Reference is made to the accompanying drawings wherein:

Figure 1 is a side elevation of the hand micrometer with a part in section.

Figure 2 is a sectional view of the anviladjustment lock, taken along the section line 2--2 of Figure -1.

Figure 3 is a top view of the hand micrometer with a part in section, taken along the section line 3-3 of Figure 1. j

Figure 4 is a sectional elevational view of the hand micrometer, taken along the section line 4--4 of Figure 3. f

Figure 5 is an exploded view, with a part in section, showing in greater detail various elements of Figure 4.

Figure 6 is an exploded view in perspective of the index plate, dial segment and rotative sleeve.

Figure 7 is a sectional view of the hand micrometer, taken along the section line 7-7 of Figure 4.

Figure 1 shows the crescent shaped frame 10, common to hand micrometers. On one end of this main frame there is a threaded anvil member 1l (see Figure 2). An anvil adjustment screw 12, with a threaded head and tapering shank, is located in the side of the main frame 10. A bore 13 in the main frame'runs through the threaded hole of the anvil member to the threaded hole of the adjustment screw. As the anvil adjustment screw is tightened in the main frame, its tapered shank exerts an increasing force on the hard metal bar 14. The bar 14, in turn forces a second bar 15, against the anvil member 11, thus xing it in place. The bar 15 is made of soft metal, such as copper, so as not to injure the threads of the anvil member.

The foregoing arrangement provides a means for adjusting the anvil member and locking it in the desired position; while, for convenience and practicality, the locking means is removed as far as possible from the working surface of the anvil member. Furthermore, this arrangement permits the anvil bearing end of the frame to be small so that the operator can measure objects in places where the usual hand micrometer with adjustable anvil member would not tit.

The other end of the crescent shaped frame terminates in a cylindrical support 16 (Figure 1), bearing the frame States Patent ICC cylinder 17 (Figure 4). An internally threaded bushing 18 is fixed in the frame cylinder by suitable means such as solder introduced 'through the hole 19. A spindle 20, having a threaded portion 21 litting the threads of the internally threaded sleeve 18, extends through the cylindrical support 16 and is oppositely disposed to the anvil member 11.

A barrel 22 is fixed by suitable means such as soldering or brazing, to that portion o'f the spindle indicated at '23, which portion is shown as being fitted with a speed screw 24.

In the conventional hand micrometer, as the .spindle turns, the barrel rides over the frame cylinder, and a graduated circular scale on the barrel coacts with an axial zero line and a graduated longitudinal scale on the frame cylinder. in the present invention however, a rotative sleeve 25, mounted over the frame cylinder 17, carries the axial zero line 26 and longitudinal scale 27 aforesaid. This sleeve can be rotated in either direction so as to cause the axial zero line 26 to coincide with the nearest marking on the circular scale 28 of vthe barrel. The extent of rotation of the sleeve need not be greater than the number of degrees between two adjacent markings on the graduated circular scale 28. Indexing means are provided for indicating a central or true Zero position of the sleeve, and the extent of departure therefrom in either the positive or negative rotative directions. Thus the indexing means for the rotative sleeve 25 provides an accurate means for interpolation between divisions of the circular scale.

In the exemplary embodiment, an index plate 29 is adjustably mounted on the frame 10 with a portion surrounding the frame cylinder 17. A pin 30 extends downwardly from the index plate into an elongated orice 31 in the frame. By means of this pin 30, the index plate is held in adjusted position by the screws 32 and 33 in the side of the main frame (see Figure 7). A dial segment 34 is rotatably mounted with respect to the index plate, having a portion surrounding the frame cylinder 17 (see Figure 4). An annular beveled edge 35 of the dial segment 34 engages an annular beveled rim 36 of the index plate, this engagement keeping the index plate and dial segment perfectly aligned. The rotative sleeve 25 fits into an annular groove 37 in the dial segment (see Fig. 6) and is xed in position therein by means of the lug 38 which engages in the slot 39. The rotative sleeve is held down in position by the circular washer spring 40 and the threaded nut 4l which engages the outer threaded portion of the internally threaded bushing 13 (see Figure 5). The lower edge of the spring 40 is beveled so as to lit into the beveled upper edge of the rotative sleeve. This beveling in combination with the beveled portions 35 and 36 of the dial segment and index plate respectively, prevents side motion of the oscillating sleeve.

In the preferred construction the internally threaded bushing is slotted as at 42. As the nut 41 is tightened on the internally threaded bushing 18 the beveled threads of the nut engage like beveled threads of the sleeve, eiectively reducing its internal diameter. In this way the amount of friction between the spindle 20 and the bushing can be adjusted, and compensation made for wear on the threaded portion of the spindle 21.

The index plate 29 is provided with two index marks 42 and 43 (see Figure 3). The dial segment 34 is provided with a scale 44 which, in this particular exemplary embodiment, comprises ten markings, the outermost designated as plus zero and minus Zero respectively, and the central marking designated as 5. The dial segment is provided with a lug 45, with a small hole 46 so that the rotative sleeve can be shifted to the right or left by hand or by an instrument such as a scriber or scratch awl.

The above construction has the advantage of providing an interpolation arrangement by simple and inexpensive means without necessitating complicated apparatus hitherto proposed'for the purpose, sometimes including more than one barrel. The instrument of this invention reduces the opportunity for the collection of dirt and lgrit within the mechanism and provides an instrument of reduced weight and bulk.

In an'exemplary method of use of this instrument the operator sets the rotative sleeve 25 at the true zero position by means of the dial segment 34 (see Fig. 1). Then, the micrometer is placed over the working piece in such a way that the part to be measured is between the anvil member 11 and the spindle 20. The barrel 22 is turned until the part to be measured is engaged between the anvil and the spindle end and the proper feel is achieved, a concept Well known to those skilled in the art. The rotative sleeve 25 is then turned either to the right or the left, by means of the dial segment 34, until the axial zero line 26 coincides with the nearest division of the scale 28. The readings of the scales 28 and 27 are then added and the reading of the dial segment scale 44 is either added to or substracted from this result, depending on the direction in which the dial segment was shifted. If he Wishes, the operator may set the instrument aside and the guards 47 and 48 on either side of the frame 10 will act to preserve the setting, by permitting the micrometer to rest on a flat surface with the moving parts out of contact with the surface.

Modiiications may be made in the invention without departing from the spirit of it.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a micrometer, a threaded spindle engaged in an internally threaded cylinder, a barrel connected to the spindle and overlying said cylinder, a circular graduated scale on said barrel, a sleeve surrounding said cylinder and lying inside said barrel, an index plate fixed to adjust the position of said index plate with respect to 4 said frame, the said scale markings on said dial segment and index plate indicating a true zero position for said sleeve, and rotative departures therefrom in the plus and minus directions, the index plate and dial segment having annular portions surrounding said cylinder and radially extending portions bearing said scale markings.

2. The structure claimed in claim l wherein projecting guard elements are attached to the frame adjacent the index plate.

3. The structure claimed in claim 1 wherein the upper portion of said internally threaded cylinder is provided with external threads, and wherein a nut is engaged with said external threads and a washer spring is located between said nut and the end of said sleeve.

4. The structure claimed in claim 1 wherein the upper portion of said internally threaded cylinder is provided with external threads, and wherein a nut is engaged with said external threads and a washer spring is located between said nut and the end of said sleeve, the externally threaded portion of said cylinder being longitudinally slotted and the engaging threads of said cylinder and nut being tapered whereby to adjust the frictional engagement'of said spindle in said cylinder.

5. A micrometer comprising a frame, a cylinder at one end of the frame, a spindle threaded into said cylinder, an anvil at the other end of said frame, an index plate having an annular portion surrounding said cylinder and a radially extending portion extending along said frame, means on said frame for fixing the rotative position of said index plate with respect to said cylinder, a dial segment having an annular portion surrounding said cylinder above and in contact with the annular portion of said index plate, and a radially extending portion overlying the radially extending portion of said index plate, a sleeve rotatively mounted on said cylinder and having a non-rotative connection with the annular portion of said dial segment, a nut and washer spring engaging an externally threaded portion of said cylinder and serving to hold said sleeve, said dial segment and said index plate in engagement and assembly, a barrel surrounding said sleeve and attached to said spindle, a circular graduated scale on said barrel, an axial zero line and longitudinal graduated scale on said sleeve, and scale markings on said dial segment and index plate.

References Cited in the le of this patent UNITED STATES PATENTS 141,915 Bonnaz Aug. 19, 1873 582,154 Clapp May 4, 1897 1,269,756 Slocomb June 18, 1918 1,840,276 Parkhurst Jan. 5, 1932 2,190,899 Vierling Feb. 20, 1940 2,666,263 Laserson Jan. 19, 1954 

